GELI question

Hello,
I am trying to install/use FreeBSD-6.0-RELEASE.
I tried to use geli command on shell to initialize hard disk.
But it seems geli command option seems different from
"Complete Hard Disk Encryption Using FreeBSD's GEOM Framework"
when i try to use "geli init -b /dev/ad0" on shell prompt, it says "Unknown command: init"
usage: geli help
geli list [name ...]
geli status [-s] [name ...]
geli load [-v]
geli unload [-v]
How can I get to work geli command? What option need to use with it?
Regards,
Balgaa